DESCRIPTION (provided by investigator): Intrapartum electronic fetal heart rate monitoring (EFM) has become the most frequently used instrument in obstetrics in the United States, despite its classification as a D by the U.S. Preventative Services Task Force, signifying the lack of evidence for benefit and the potential for harm. EFM rapidly gained ubiquitous use prior to evidence of benefit from properly conducted research. Today, despite the available evidence that EFM does not reduce the rate of cerebral palsy or stillbirth, its use is widespread; intrapartum EFM was used in 3,585,390 births in the U.S. in 2005. At a joint consensus conference in May of 2008 sponsored by the American College of Obstetricians and Gynecologists (ACOG), the Society of Maternal Fetal Medicine (SMFM), and the Eunice Kennedy Shriver Nation Institute of Child Health and Human Development (NICHD) the leading experts in obstetrics and fetal monitoring re-convened to prioritize areas for research and to reevaluate the definitions that were set forth by a similar group 11 years before. The group acknowledged that no evidence had emerged on EFM since the 1997 consensus conference, despite the ubiquitous use of EFM, and again called for well-designed studies to fill the significant knowledge gaps which continue to exist1. One of the areas of highest importance sited was observational studies focused on indeterminate EFM patterns, which is addressed in this proposed study. Fetal heart rate decelerations are the most common component of indeterminate EFM patterns seen in daily clinical practice. To better understand the relationship between fetal heart rate decelerations and fetal academia, this proposed cohort study of over 7,000 women examines the predictive value of characteristics of fetal decelerations, using novel and established measures, for fetal academia and early evidence of neonatal neurologic injury. The specific aims of this proposed project are to estimate the association between indeterminate EFM recordings, particularly fetal heart rate decelerations, and fetal academia (measured by arterial umbilical cord gas analysis at delivery), academia subtypes, and measures of neonatal cerebral injury. The study uses standard and novel ways to assess the EFM recordings of women during the 120 minutes prior to delivery and assess their association with or predictive ability for fetal academia, alone or in combination. Ultimately the goal is to develop and validate a clinical predictive index for fetal academia and neonatal cerebral injury based on features of EFM encountered everyday in clinical practice, for which the meaning is currently unknown. This study will address an issue of priority for NICHD, and more importantly, an issue of priority for the health of women and their children.